Trend and bar graph displays provide a readily understood representation of numeric data. A bar graph for example can illustrate the current value of one or more scalar variables. A trend illustrates several scalar values of a variable as a function of an independent variable. One typical trend display is to plot the scalar values of a variable as a function of time, although other independent variables may also be used.
Trend and bar graphs were in the past laboriously plotted by hand. More recently, trend and bar graphs were automated to the extent that graphics printers were used to produce hard copy representations of trend and bar graphs. Plotting trends and bar graphs on video display terminals is also within the scope of the prior art. Early examples of producing trend or bar graph information on a video display terminal can be found in Metz et al 3,648,270 for Graphic Display System and Lehari et al 3,725,901 for Method and Apparatus for Representing Measured Values on the Screen of a Video Apparatus. Both patents describe electronic circuits which when associated with a video display terminal can be used to provide trend and bar graph information.
Later devices providing for trend and bar graph displays use or are associated with digital computers or digital processors, see in particular Bickley et al 4,283,723; Williamson, Jr. et al 4,303,973; Hamada et al 4,307,393; Hara et al 4,231,032 and Ricketts et al 4,375,079.
To the extent that devices disclosed in the aforementioned patents produce trend or bar graph displays, those displays are presented in a format, orientation and size which is predetermined. In some cases, see for example Williamson, Jr. et al 4,303,973, the operator can select particular variables for display, and in some cases even select the number of different variables which will be displayed, see the selection described in col. 20 for selecting 1-4 variables in a quarter-screen format, or up to 2 variables in a half-screen format. It should be apparent, however, that this limited flexibility does not provide a display system suited in many applications.
For example, an operator may desire to display a bar graph or trend of a single scalar variable, but also include unique graphics associated with the bar or trend display. Depending upon the particular graphics employed, the operator may desire the bar graph or trend to be located at any point on the display and occupy any selected sub-region of the display area. The prior art does not teach a system which allows the operator to freely select the location of a trend or bar display as well as to freely define the extent of the region of the display which will be occupied by the trend or bar graph (from 0% to 100%). Likewise, the operator may desire to produce a display based on more than a single scalar variable with the trend or bar graph of each variable located independently of other variables and of a size which is independent of the size of the trend or bar graph for other variables.
Typical systems for generating displays of trend or bar graph information have in the past included a mainframe computer, a large bulk memory system including tape units, rigid disk units and removable disk pack units, high resolution cathode ray tube (CRT) displays, a large random access memory (RAM) of sufficient capacity to store the graphics information and address each pixel of the high resolution display, and input/output (I/O) devices such as sensors, digitizer pads with cursors and plotters. These systems are very expensive but that cost could be justified because of the extreme capability. More recently the prices of such large systems have come down significantly due to economies of computer and memory system manufacture, and because of that such systems are being applied to a wide variety of applications. Nevertheless, large-scale systems are still quite expensive and their use is generally limited to correspondingly expensive applications. For example the system described in the Williamson, Jr. et al patent is arranged to control a large-scale industrial process.
At the other end of the spectrum are the so-called personal computers based on microprocessors which have been developed over the past decade. These typically comprise a mother board containing the microprocessor, a read only memory (ROM) encoded with a basic input/output system (BIOS) for controlling the microprocessor, a limited amount of RAM and a number of adpaters for interfacing with various I/O devices. These I/O devices may include a Keyboard, a medium or high resolution CRT display, one or more floppy disk drives, and a printer such as one of the more popular dot matrix printers. Although personal computers are small and compact, they are capable of some fairly sophisticated applications. They are especially well-suited to business applications such as accounting, data base management and business analysis. Recently, a number of business applications have been developed which include graphic support. These applications take the input or calculated numerical data and produce line graphs, bar charts and pie charts which are much easier to interpret than the raw numerical data. Prints of these graphical dislays are made by reading out the data shown on a CRT to a dot matrix printer provided with a graphical capability or to an inexpensive pen plotter. The latter device is also capable of generating tansparencies for use in overhead projectors. The acceptance of business applications with graphic support has been immediate and substantial, with the result that there is a considerable demand for graphics applications which are not necessarily limited to business graphics. The ability to generate schematic diagrams, flow charts, floor plans, and similar graphic displays would be highly desirable in the production of technical manuals, advertising layouts and the like. The presentation of trend and bar graphs is one element in satisfying the demand. However, this ability should be accompanied by the flexibility to locate the trend or bar graph, at will, and to freely select the portion of the total display which will be occupied by the trend or bar graph.